Portable loop aerial



April 22, 1930. ANDREWS 1,755,530

PORTABLE LOOP AERIAL Filed April 2, 1923 f 2/6227? Faward/ZflrzarewaPatented Apr. 22, 1930 UNITED? STATES EDWARD F. ANDREWS,

OF CHICAGO, ILLINOIS PORTABLE LOOP AERIAL Application filed. April 2,

My invention relates to loop aeria-ls and is directed more particularlyto portable loop aerials, an object being to provide a loop aerial whichis light, strong and attractive in appearance, which will pivot on itsbase and can be readily separated therefrom, at the same time makingcontact with terminals on the base; and which will be simple and easilymanufactured, at a comparatively low cost.

A feature of my invention is the provision of a loop aerial having smallexternal dimensions with a maximum length of wire and small capacity andinductance changes.

Another feature of my invention is the provision of an aerial loop inwhich the wires,

although supported only on the radially extending arms of the frame, aremaintained under a continuous tension, to automatically take up anyslack that might otherwise result from stretching.

There are other features of my invention and these will be moreparticularly pointed out in the ensuing part of the specification andappended claims.

For a better understanding of my invention reference is to be had to theaccompanying drawing, in which Fig. 1 is a side elevation of thepreferred form of my invention;

Fig. 2 is a top plan view of Fig. 1;

Fig. 3 is a vertical sectional view along the line 3-3 of Fig. 1; I

Fig. 4 is an enlarged end view of one of the arms, showing the method ofcutting the 5 circular or curved-bottom slots therein; and

Fig. 5 is a sectional view along the line 5-5 of Fig. 4.

Referring now more in detail to my invention as shown, I provide acentral frame having a plurality of arms 7 extending radially in asingle plane, said arms having sockets in which the loop supporting arms8 extend. The frame 7 is preferably made of metal and I use aluminum forthis purpose, as it is light.

The arms 8 are preferably of a nonconducting material, and I use woodfor this purpose. The lower arm 8 is preferably driven tightly into itssocket, while the other three arms 8 are slidably supported in theirsockets, with a spring 9 positioned in the socket and 1923. Serial No.629,322.

tending to press the arms outwardly. This gives a relative outwardmovement of the arms, so as-to hold the wire wound thereon under acontinuous tension and prevent sagging, which would otherwise occur fromthe stretching thereof. By holding the wires taut in this way, thechange in capacity and inductance effects of one wire upon the other isreduced to a minimum. If these wires were. permitted to sag andmaterially change their relative distances apart, the capacity andinductance of the entire aerial would change, and this, of course, isobjectionable.

Now as to the aerial loop, I preferably by my improved construction andarrangement provide a loop aerial having small external dimensions, andat the same time having each turn of the wire upon it include themaximum enclosed area consistent with the external dimensions of theaerial, at the same time maintaining a proper separation of each wirefrom the other. To this end I provide two spiral windings, one placedupon each side of the supporting arms, preferably starting one windingat the bottom of the supporting stick 8' at 10, and winding the spiralinwardly, or toward the center of the loop, until half the number of thedesired turns have been put on, then crossing the wire over to theopposite side of the frame and winding it spirally outwardly until itterminates at the lower end of the supporting stick 8' at 11, and whichis opposite the starting point 10 of the opposite coil.

Another; advantage of my improved coil arrangement is that the device isevenly balanced, and also maintains a balanced pres sure upon the sticksby the springs 9.

It will also be seen that by the use of the coils on opposite sides ofthe frame, the mean area enclosed by all the turns is considerablyincreased, without any increase in the external outside dimensions ofthe device, as the width is of course determined by the thickness of thesupporting arms, which would be practically the same for a single spiralas for the double spiral. For the purpose of supporting the wire uponthe frame, I provide a novel means in the form of curved slots thebottoms of which are curved where they support the wire, therebyeliminating any sharp kinks in the wire and permitting the wire toreadily slide therein as he sticks are pressed outward y, to maintainthe loops taut.

These curved slots are cut in the arms preferably by means a hollowmilling cutter, or hollow circular saw, 12. In cutting these slots Ipreferably hold the sticks on the table of a drill press, setting thesticks at the proper angle, and then feeding the cutter 12 down into thesticks to cut the slots 13. By reason of the peculiar cutter used, aidedby the angle at which the slots are cut, I provide arounded bottom inwhich the wire readily slides and 1s supportedat a gradual bend, withoutany sharp angles at the supporting points.

preferably arrange the aerial loop por- $1011 of the device so that itmay rotate on a base, and to this end I insert a pivot pin 14 into theend of the stick 8, which pin sets mto a metallic socket 15, carried inthe base 16. The pin preferably rests upon its end, so as to support theweight of the device at this point. The pin 14 also acts as a terminalfor the loop, the end 10 of the wire being fastened to a terminal clip16, connected with the pin 14 by a screw 17.

In order to provide a second. connection from the loop to the base 16,and one which Wlll act as a good conductor although permitting rotationof the aerial, I secure a metallic ferrule 18 to the bottom of the stick8, and connect the end 11 of the loop there with by means of a terminalconnector 19. This ferrule 18 not onlyacts as contactor for the loop,but also protects the end of the stick 8 which is made of a smalldiameter and thus readily chipped or cracked at the bottom.

In order to extend a connection fro n the ferrule 18 to the base, Iprovide a spring member 20 fastened to the bottom of the base and havinga portion 21 extending up through the base, adapted to be engaged by theedge of the ferrule 18. The tension of spring 20 is such that it willpermit the aerial pin M to rest in the bottom of the socket 155, butstrong enough to maintain a good sliding contact with the ferrule, andat the same time not interfere with a free rotation thereof.

The socket 15 and spring member 20 are connected to suitable bindingposts 22 and 23, respectively, so that the device may be readilyconnected as desired.

It will also be seen that the aerial member may be readily lifted out ofthe base 24 and plugged into a suitable socket in a desk or radio set,or wherever desired.

In winding the loops upon the framework I preferably hold the frame in asuitable with the sticks placed inwardly against the tension of springs9. The wire is then wound thereon and fastened to the terminals l6l9.The device is then removed from the jig and the springs 9 are free topress the arms outwardly and hold the wire under a constant pressure.

A feature of my loop aerial is that it may be shipped knocked down butreadily assembled without the use of any special jigs, tools, ormachinery. To this end the arms, central cross-piece or support, wireand base are shipped separated, and to assemble the parts the arms arefirst inserted in the sockets of the central cross piece or frame, withthe springs 9 in place. It is understood, of course, that the wire isnotyet wound on the frame. The three spring-pressed arms 8 are then pushedinto the sockets until the holes 26 in the arms 8 andthe holes 27 in theframe arms register. I then stick a nail or wire rod through the holesto hold the arms against the tension of the springs 9. The wire 11 isnow wound on the supporting arms and secured at its terminals 16'-19.The nails are then withdrawn from the holes in the arms, thus permittingthe springs 9 to act upon the arms 8 and press them outwardly, therebymaking the wire taut and holding it under constant pressure. 7

In the preferred form of constructmg and winding my improved loopaerial, there are certain electrical advantages arising moreparticularly from the opposed spiral windings, but it is thoughtunnecessary to go into the matter, as these will be readily apparentfrom the use of the device.

What I claim as new and desire to secure by United States Letters Patentis:

I 1. In a loop aerial, a central frame having fourfixed radiallyextending sockets therein, one for each supporting arm of the device,aerial wire supporting arms extending outwardly from said sockets, anaerial loop spirally supported upon said arms, and resilient meanspressing outwardly upon one or more of said arms to hold the loop undertension and prevent slack therein.

2. In a loop aerial, radially extending loop supporting arms. said armshaving curvedbottom inwardly slanting slots cut in the side thereof forsupporting the loop wire with a gradual bend in the plane of the loop.

3. In a loop aerial, radially extending loop supporting arms, said armshaving curved slots in the side formed so as to have the slots slantinwardly with a curved bottom to support the loop wire with a gradualbend in the plane of the loop.

4:. In a loop aerial, a base having a vertical conducting sockettherein, a contact member in the base adjacent the socket, a loopsupport having a downwardly extending conducting plug for insertion inthe base socket and by which the support may turn, an aerial loop onsaid support, a ferrule at the bottom of support surrounding the plugand for slidingly contacting with the base contact,

and means for connecting the terminals of an aerial loop with the plugand ferrule.

5. In a loop aerial, a frame comprising radially disposed arms havingwire supporting means on opposite sides at the outer ends thereof, and aloop supported by said means comprising two spiral windings one on eachside of the arms, one winding starting at the outer end of a supportingone of said arms and continuing spirally toward the center, thencrossing to the other side and continuing spirally outward, terminatingat said supporting arm, terminals on said arm to which the ends of thetwo windings are secured, one of said terminals being a plug and theother a ferrule on the arm, said plug being adapted to act as a pivot bywhich the aerial may turn.

6. In a loop aerial, a frame comprising radially disposed arms havingwire supporting means on opposite sides at the outer ends thereof, and aloop supported by said means comprising two spiral windings one on eachside of the arms, one winding starting at the outer end of a supportingone of said arms and continuing spirally toward the center, thencrossing to the other side and continuing spirally outward, terminatingat said supporting arm, terminals on said arm to which the ends of thetwo windings are secured, a two-contact swivel plug at the end of thesupporting arm to which said winding ends are connected, and acooperating two-contact jack for the plug, in which the aerial may turn.

7. The method of providing wire supporting slots for a loop aerialsupporting arm which consists of cutting a circular slot angularly intothe side of the arm.

8. In a loop aerial, a loop support having a downwardly extendingsupport, a ferrule on the end of said support and a central plugtherein, said ferrule and plug acting as contact terminals for the loop,a base, terminals on the base, and a socket for rotatably hold ing thesupport in the base including stationary contact means for electricallyconnecting the ferrule and plug with said terminals.

9. In a loop arial, a frame comprising radially disposed arms havingwire supporting means along opposite sides thereof, and a loop supportedby said means comprising a continuous winding of two spirals, one oneach side of the arms, and wound so that the traversing current willflow from the outer end of one spiral toward the center and then over toand from the center of the other spiral toward the outer end, and in alike direction spirally in both spirals on the same axis.

In witness whereof, I hereunto subscribe my name this 8th day of March,A. D. 1923.

EDWARD F. ANDREWS.

